1. The official calculation method of ventilation duct resistance:
The latest version of ventilation duct resistance calculation is based on the method provided in the Design Manual for Use of Heating and Air Conditioning compiled by Lu Yaoqing.
2. Data input:
Duct Size: Enter the diameter of the circular pipe and the side length of the rectangular pipe.
Air volume: the air volume in the air duct.
Duct Length: If a duct length is given, it
The total resistance of the segment is calculated.
3. Result output:
After data input, press the "Calculate" button, and the calculation result will be given in the result output column.
There are two kinds of air flow resistance in the air duct. One is the energy loss along the way due to the viscosity of the air itself and the friction between the air and the pipe wall, which is called friction resistance or along the way resistance; The other is that when the air flows through the pipe fittings and equipment in the air duct, the relatively concentrated energy loss caused by the change in the size and direction of the flow velocity and eddy current is called local resistance.
Calculation and principle of friction resistance of ventilation pipe:
According to the principle of fluid mechanics, the friction resistance of air flowing in the pipe with constant cross section shape is calculated as follows:
Δ Pm= λν two ρ l/8Rs
For circular air duct, the friction resistance calculation formula can be rewritten as follows:
Δ Pm= λν two ρ l/2D
The friction resistance (specific friction) per unit length of circular air duct is:
Rs= λν two ρ/ 2D
Among the above
λ———— Friction resistance coefficient
ν———— Average velocity of air in air duct, m/s;
ρ———— Air density, Kg/m3;
L -- length of air duct, m
Rs -- hydraulic radius of air duct, m; Rs=f/P
F -- cross-sectional area of fluid filled part in the pipeline, m2;
P -- wet perimeter, which is the perimeter of air duct in ventilation and air conditioning systems, m;
D -- diameter of circular air duct, m.
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